1. Field of the Invention
The present invention relates to a projection apparatus, and particularly to a projection apparatus including a positioning and fixing structure of an optical prism holder and lens holder.
2. Description of the Related Art
In a projection apparatus using, for example, a plurality of light valves of liquid crystal, a white light beam is separated into color light beams of red, green and blue of the three primary colors, the color light beams are image modulated by the liquid crystal light valves, and next, the respective color light beams are synthesized to generate a light flux, and then, it is projected onto a screen by a projection lens.
FIG. 1 is a plan view showing a conventional projection apparatus. Liquid crystal panels 1001, 1002 and 1003 are provided on three planes of a prism 1000, respectively. The liquid crystal panel 1001 is a transmission type optical modulation element for green (G), the liquid crystal panel 1002 is a transmission type optical modulation element for blue (B), and the liquid crystal panel 1003 is a transmission type optical modulation element for red (R).
These liquid crystal panels 1001, 1002, and 1003 are positioned and fixed to the prism 1000 by stages 1004, 1005 and 1006, respectively. This prism 1000 is fixed at the side of a projection lens holder 1014 of a projection lens 1010.
FIGS. 2 to 4 show structural examples of the stages 1004 to 1006.
Positioning (registration) of the three liquid crystal panels 1001, 1002 and 1003 is performed in such a manner that one liquid crystal panel (here, the liquid crystal panel 1001 for green) is mechanically set so that the center of the liquid crystal panel 1001 can be located at the center of the prism 1000 and the projection lens 1010, and then, simple stages with adjustable X, Y, Z and xcex8 axes for the other two liquid crystal panels 1002 and 1003 are finely adjusted with the liquid crystal panel 1001 for green as a basis, and while the Z axis is adjusted, positioning is performed so that images of the three liquid crystal panels 1001, 1002 and 1003 of red, green and blue overlap on a screen. At this time, accuracy of ⅓ pixel to 1 pixel is required for the positioning accuracy of the three liquid crystal panels.
Japanese Patent No. 2714939 proposes a method in which a polarizing plate is stuck onto each of three planes of a cross dichroic prism, a jig is used to position a liquid crystal panel on the polarizing plate, and the liquid crystal panel is directly fixed to the prism.
In the foregoing liquid crystal projection apparatus, the simple adjusting stages 1004 to 1006 are prepared correspondingly to each of the liquid crystal panels, the stages are fixed to the cross dichroic prism, and the adjustment of positioning is performed. Thus, there have been problems as follows:
(1) Since the stages for adjustment are provided for the respective liquid crystal panels of red, green and blue, the number of parts becomes large.
(2) After adjustment with respect to the X, Y, xcex8, and Z axes is performed, the stage is fixed by a screw or the like so that it does not move. When the screw is tightened to fix, the stage slightly moves and causes a positional deviation of the liquid crystal panel.
(3) if an attempt is made to adjust the positional relation of the respective liquid crystal panels with accuracy, an adjustment mechanism of the stage becomes complicated, and adjustment axes are increased, so that an optical system becomes large.
(4) It becomes difficult to secure a gap between the outgoing side of the liquid crystal panel and the prism plane, so that air comes not to pass between the liquid crystal panel and the prism, cooling efficiency of the liquid crystal panel is poor, and the liquid crystal panel comes not to function correctly.
(5) Since the stage is constructed such that it is fixed by being always pulled by a spring or the like in one direction, it is weak against shock, and the positional deviation of the liquid crystal panel is apt to occur by vibration, shock, or the like.
(6) When the respective liquid crystal panels for red, green and blue are positioned with higher accuracy, it takes a time to position the three liquid crystal panels.
In the method of Japanese Patent No. 2714939, the polarizing plate stuck on the prism can not be cooled, so that its temperature becomes high by light from a light source (lamp), the polarizing function of the polarizing plate is lost, and the optical modulation at the liquid crystal panel becomes impossible.
Besides, if the liquid crystal panel is directly bonded onto the polarizing plate by an adhesive, when the adhesion is peeled for replacement of parts in the case where a defect occurs in the polarizing plate, the liquid crystal panel or the like, the parts of the polarizing plate and the liquid crystal panel are damaged, and usable parts are also damaged and become wasted.
Then, the present invention has been made to solve the above problems and an object thereof is to provide a projection apparatus which adopts a simple structure and can be assembled, while positioning of an optical modulation element, a synthesizing prism and a projection lens is made with accuracy and without fail.
According to a first aspect of the present invention, a projection apparatus includes a light source, separation optical means for color separating a light beam from the light source into a plurality of color light beams, a plurality of transmission type optical modulation elements for modulating the separated color light beams, synthesis optical means for generating a light flux by synthesizing the respective color light beams modulated by the optical modulation elements, and projection optical means for projecting the synthesized light flux, wherein the projection apparatus further comprises a prism holder for holding a synthesizing prism as the synthesis optical means, the prism holder including a first positioning portion, and being positioned and fixed to one end plane and the other end plane of the synthesizing prism opposite to each other, except for incidence planes of the synthesizing prism on which the respective color light beams are incident and an outgoing plane of the synthesizing prism for outputting the synthesized light flux to the side of the projection optical means, and a lens holder for holding the prism holder and a projection lens as the projection optical means, the lens holder including a second positioning portion which is fitted to the first positioning portion to make positioning and fixing.
The prism holder holds the synthesizing prism as the synthesis optical means. The prism holder includes the first positioning portion, and is positioned and fixed to the one end plane and the other end plane of the synthesizing prism opposite to each other, except for the incidence planes of the synthesizing prism on which the respective color light beams are incident and an outgoing plane of the synthesizing prism for outputting the synthesized light flux to the side of the projection optical means.
The lens holder holds the projection lens as the projection optical means. The lens holder includes the second positioning portion which is fitted to the first positioning portion of the prism holder to make positioning and fixing.
By this, the prism holder is positioned to the one end plane and the other end plane of the prism and can fix the synthesizing prism. The second positioning portion of the lens holder can be fixed while positioning is made, by using and fitting the first positioning portion of the prism holder.
Like this, although the structure is simple, the lens holder and the prism holder, and the projection lens and the synthesizing prism can be fixed and assembled while positioning is made without fail.
According to a second aspect of the present invention, in the foregoing projection apparatus, the first positioning portion of the prism holder includes a positioning hole, the second positioning portion of the lens holder includes a positioning pin which is inserted in the positioning hole to position the prism holder with respect to the lens holder, and the lens holder and the prism holder are fixed by screwing after positioning.
The first positioning portion of the prism holder includes the positioning hole, and the second positioning portion of the lens holder includes the positioning pin which is inserted in the positioning hole to position the prism holder with respect to the lens holder. By this, by inserting the positioning pin in the positioning hole, the prism holder and the lens holder can be easily positioned. The lens holder and the prism holder are fixed by screwing after positioning.
According to a third aspect of the present invention, the projection apparatus of the first aspect includes a first fixing member which is disposed opposite to one of the three incidence planes on which the color light beams of the synthesizing prism are incident, is bonded to the one end plane and the other end plane of the synthesizing prism, and includes an opening portion through which the color light beams modulated by the optical modulation element pass, and a plurality of ear-shaped protrusions; and a second fixing member which is put into close contact with and is fixed to the first fixing member so that the optical modulation element is fixed to the side of the synthesizing prism, includes an opening portion through which the color light beams modulated by the optical modulation element pass, and a plurality of ear-shaped protrusions, wherein the protrusions of the first fixing member and the protrusions of the second fixing member are fixed by bonding or soldering in a state where the three optical modulation elements are respectively positioned to the three incidence planes of the synthesizing prism on which the color light beams are incident so that the color light beams form the light flux synthesized by the synthesizing prism.
The first fixing member is disposed opposite to one of the three incidence planes, and is bonded to the one end plane and the other end plane of the synthesizing prism. The first fixing member includes the opening portion through which the color light beams modulated by the optical modulation element pass, and the ear-shaped protrusions. The second fixing member is put into close contact with and is fixed to the first fixing member so that the optical modulation element is fixed to the side of the synthesizing prism. The second fixing member includes the opening portion through which the color light beams modulated by the optical modulation element pass, and the ear-shaped protrusions.
The protrusions of the first fixing member and the protrusions of the second fixing member are fixed by bonding or soldering in the state where the three optical modulation elements are respectively positioned to the three incidence planes on which the color light beams of the synthesizing prism are incident so that the color light beams reproduce the light flux synthesized by the synthesizing prism.
According to a fourth aspect of the present invention, in the projection apparatus of the third aspect, the adhesive is a photo-curing adhesive.
By using the photo-curing adhesive, bonding can be easily made.